Colorless glasses/borosilicate glasses with special UV-edge

Abstract

A borosilicate glass, having a spectral edge situation in a UV range of 280 to 325 nm, which can be set in a simple and defined manner, with the composition in percent by weight on an oxide basis of 60-75% SiO2, 10-15% B2O3, 5-15% Na2O, 5-10% K2O, 0-5% Li2O, 0.1-1 CaO, 0.5-3% BaO, >0-1.7% TiO2, 0-0.5% Sb2O3, and normal refining agents.

Description

[0001] 1. Field of the Invention[0002] This invention relates to a borosilicate glass with a special edge situation and to uses for the borosilicate glass.[0003] 2. Discussion of Related Art[0004] In order to filter, in a targeted manner, a UV range which generally is defined as below 400 nm and can be divided into three sub-ranges, UVA, UVB and UVC, so-called colorless glasses or also optical glasses with defined edge situations are used. The edge situation or edge wavelength .lambda..sub.c corresponds to half of the pure transmission maximum value between the blocking and permeable range.[0005] A spectacle glass is known from European Patent Reference EP 0 151 346 B1 which has a UV edge in the range between 325 nm and 335 nm. TiO.sub.2 is added to the glass for this purpose. The proportion of TiO.sub.2 is thus 4-6% by weight on an oxide basis.[0006] This type of glass is not suitable for commercial application cases, in which a dimensional stability even at high transformation tem...

AI Technical Summary

Benefits of technology

[0020] The continuous production with edge situations .lambda..sub.c of 280 to 325 nm is essential for these glasses. This continuous production is ensured because of the uniform base glass. TiO.sub.2 is used as doping for the desired steep edge situation, an addition not required in the case of very low edge situations <290 nm. This type of production saves costs and time, for example it avoids long remelting phases, in which no usable glass is produced.

[0029] The glass can also be free of PbO and of As.sub.2O.sub.3 apart from unavoidable impurities. The glass can thus be free of toxic components and therefore can be ecologically harmless.

Problems solved by technology

This type of glass is not suitable for commercial application cases, in which a dimensional stability even at high transformation temperatures, for example <560.degree. C., and / or a stable expansion coefficient is required.

The CeO.sub.2 significantly increases the material costs in the glass.

In addition, CeO.sub.2 has a negative effect on the solarization of the glass.

Exact UV edges and optical situations cannot be set with this glass.

Consequently, glasses with high transmission in the pass range are not possible.

The glass taught by German Patent Reference DE 38 22 733 A1 does not make it possible to set a defined UV edge situation.

However, the UV edge situation or the optical properties are not relevant for these glasses.

This type of production saves costs and time, for example it avoids long remelting phases, in which no usable glass is produced.

Higher contents would impair the meltability, in the case of lower contents, would make the glass formation difficult.

Lower SiO.sub.2 proportions in the glass would also result in Abb numbers which are too low.

With alkali contents which are too high, above all the hydrolytic resistance would be impaired, but also to a lesser extent the resistance to alkali liquor.

However more than 1.7% by weight of TiO.sub.2 in the glass scarcely still effects a noticeable displacement of the UV edge in the longer-wave range in this glass system and promotes devitrification.

In addition, too high contents of TiO.sub.2, as indicated, would increase the refractive index too greatly and reduce the Abb number too greatly.

Images